LOCATION FERGUS MT+WYEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Vertic Argiustolls
TYPICAL PEDON: Fergus clay loam, cultivated. (Colors are for dry soil unless otherwise noted)
Ap--0 to 4 inches; brown (7.5YR 5/2) clay loam, dark brown (7.5YR 3/2) moist; moderate medium granular structure; slightly hard, friable, sticky and plastic; many very fine roots; neutral (pH 7.2); abrupt smooth boundary. (4 to 10 inches thick)
Bt1--4 to 9 inches; dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine angular blocky structure; hard, friable, sticky and plastic; many very fine roots; many fine pores; many distinct clay films on faces of peds; neutral (pH 7.2); clear smooth boundary.
Bt2--9 to 28 inches; reddish gray (5YR 5/2) clay loam, reddish brown (5YR 4/3) moist; moderate medium and coarse prismatic structure parting to moderate medium and coarse blocky; hard, friable, sticky and plastic; many to few very fine roots; many fine pores; many distinct clay films on faces of peds; slightly alkaline (pH 7.6); abrupt smooth boundary.
Bt3--28 to 34 inches; reddish brown (5YR 5/3) clay loam, reddish brown (5YR 4/3) moist; moderate medium blocky structure; hard, friable, sticky and plastic; few fine roots; few fine pores; 10 percent pebbles; many distinct clay films on faces of peds; few fine threads of lime; slightly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (combined Bt horizons 16 to 34 inches thick)
Btk--34 to 40 inches; reddish brown (5YR 5/3) silty clay loam, reddish brown (5YR 4/3) moist; moderate coarse blocky structure; hard, friable, sticky and plastic; few fine roots; few fine pores; common distinct clay films on faces of peds; common medium masses and threads of lime; strongly effervescent; moderately alkaline (pH 8.4); clear smooth boundary. (0 to 15 inches thick)
Bk--40 to 60 inches; reddish brown (5YR 4/3) clay loam, dark reddish brown (5YR 3/3) moist; massive; hard, friable, sticky and plastic; common fine and medium masses of lime; moderately effervescent; strongly alkaline (pH 8.6).
TYPE LOCATION: Judith Basin County, Montana; 2,340 feet east and 900 feet north of the SW corner of sec. 4, T. 17 N., R. 9 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 7 to 15 inches.
Depth to Bk horizon - 20 to 36 inches.
Ap horizon - Hue: 5YR, 7.5YR, 10YR
Value: 3, 4, or 5 dry; 2 or 3 moist
Texture: loam, silt loam, clay loam, silty clay loam
Clay content: 20 to 35 percent
Rock fragments: 0 to 15 percent pebbles
Reaction: pH 6.6 to 7.8
Bt1 horizon - Hue: 7.5YR, 5YR, 10YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 2 or 3
Texture: clay loam, silty clay loam, clay
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent pebbles
Reaction: pH 6.6 to 7.8
Bt2 horizon - Hue: 2.5YR, 5YR, 7.5YR
Value: 4 or 5 dry, 4 or 3 moist
Chroma: 2, 3, 4, or 6
Texture: clay loam, clay, silty clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent pebbles
Reaction: pH 6.6 to 7.8
Bt3 horizon - Hue: 2.5YR, 5YR, 7.5YR
Value: 4, 5, or 6 dry; 3, 4, or 5 moist
Chroma: 2, 3, 4, or 6
Texture: clay loam, clay, silty clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent pebbles
Reaction: pH 7.4 to 8.4
Btk horizon - Hue: 2.5YR, 5YR, 7.5YR
Value: 4, 5, 6, or 7 dry; 3, 4, or 5 moist
Chroma: 2, 3, 4, or 6
Texture: silty clay loam, clay loam, clay
Clay content: 27 to 45 percent
Rock fragments: 0 to 15 percent pebbles
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 9.0
Bk horizon - Hue: 2.5YR, 5YR, 7.5YR
Value: 4, 5, 6, or 7 dry; 3, 4, or 5 moist
Chroma: 2, 3, 4, or 6
Texture: silty clay loam, clay loam, or clay
Clay content: 27 to 45 percent
Rock fragments: 0 to 15 percent pebbles
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 9.0
COMPETING SERIES:
Barela (NM) - has a lithic contact at depths of 40 to 60 inches.
Capillo (NM) - does not have a horizon of carbonate accumulation; has a paralithic contact at depths of 40 to 60 inches.
Charo (NM) - is 20 to 40 inches deep over basalt bedrock; does not have a horizon of secondary carbonate accumulation.
Darret (MT) - has a paralithic contact at depths of 20 to 40 inches.
Microy (NM) - is 20 to 40 inches deep over basalt bedrock; does not have a horizon of secondary carbonate accumulation.
Moreno (NM) - has high chroma mottled in the lower part of the argillic horizon and in the C horizon.
Pino (NM) - has an argillic horizon less than 12 inches thick.
Terrad (MT) - has a paralithic contact at depths of 20 to 40 inches.
Turkeysprings (NM) - has carbonates throughout the soil.
Wilcoxson (NM) - has a lithic contact at depths of 40 to 60 inches.
Zau (CO) - is 20 to 40 inches deep to a paralithic contact.
GEOGRAPHIC SETTING:
Landform - stream terraces; alluvial fans; moraines; and mountains.
Elevation - 3,000 to 6,200 feet.
Slope- 0 to 60 percent.
Parent material - alluvium; colluvium; till.
Climate - cold winters; moist springs and falls; warm summers.
Mean annual precipitation - 15 to 19 inches.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 70 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained. Moderately slow permeability. Runoff is negligible to high depending on slope.
USE AND VEGETATION: Fergus soils are used mainly as rangeland and dryland cropland. Potential native vegetation is mainly bluebunch wheatgrass, green needlegrass, western wheatgrass, and perennial forbs.
DISTRIBUTION AND EXTENT: Fergus soils are of moderate extent in the foothills and intermountain valleys of central Montana and parts of Wyoming.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Lincoln County, Wyoming, 1945.
REMARKS: Soil interpretation records: MT0096, MT8133, MT0916.
Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of 9 inches (Ap and Bt1 horizons); argillic horizon - the zone from 4 to 40 inches (Bt1, Bt2, Bt3 and Btk horizons); horizons of carbonate accumulation - the zone from 34 to 60 inches (Btk and Bk horizons); particle-size control section - the zone from 4 to 24 inches (the upper 20 inches of the argillic horizon) (Bt1 and Bt2 horizons). Fergus soils have an ustic moisture regime and a frigid temperature regime.